This invention relates to ink jet printheads. More particularly, the invention relates to an ink jet print head having a nozzle array wherein each nozzle has a moving nozzle with an externally arranged actuator.
Our co-pending U.S. patent application Serial No. 09/112,821 discloses a moving nozzle generally. Such a moving nozzle device is actuated by means of a magnetically responsive element for effecting displacement of the moving nozzle and, in so doing, to effect ink ejection.
A problem with this arrangement is that it is required that parts of the device be hydrophobically treated to inhibit the ingress of ink into the region of the actuator.
A moving nozzle-type device is proposed where the need for hydrophobic treatment is obviated.
According to the invention, there is provided an ink jet printhead which includes
a substrate;
at least one nozzle, defining a nozzle opening, arranged on the substrate, the nozzle opening being in communication with a nozzle chamber and said at least one nozzle being displaceable relative to the substrate for effecting ink ejection from the nozzle chamber through the nozzle opening, on demand; and
an actuator arranged externally of the nozzle and connected to the nozzle for controlling displacement of the nozzle.
In this specification, the term xe2x80x9cnozzlexe2x80x9d is to be understood as an element defining an opening and not the opening itself.
The nozzle may comprise a crown portion, defining the opening, and a skirt portion depending from the crown portion, the skirt portion forming a first part of a peripheral wall of the nozzle chamber.
The printhead may include an ink inlet aperture defined in a floor of the nozzle chamber, a bounding wall surrounding the aperture and defining a second part of the peripheral wall of the nozzle chamber. It will be appreciated that said skirt portion is displaceable relative to the substrate and, more particularly, towards and away from the substrate to effect ink ejection and nozzle chamber refill, respectively. Said bounding wall may then serve as an inhibiting means for inhibiting leakage of ink from the chamber. Preferably, the bounding wall has an inwardly directed lip portion or wiper portion which serves a sealing purpose, due to the viscosity of the ink and the spacing between said lip portion and the skirt portion, for inhibiting ink ejection when the nozzle is displaced towards the substrate.
Preferably, the actuator is a thermal bend actuator. The thermal bend actuator may be constituted by two beams, one being an active beam and the other being a passive beam. By xe2x80x9cactive beamxe2x80x9d is meant that a current is caused to flow through the active beam upon activation of the actuator whereas there is no current flow through the passive beam. It will be appreciated that, due to the construction of the actuator, when a current flows through the active beam it is caused to expand due to resistive heating. Due to the fact that the passive beam is constrained, a bending motion is imparted to the connecting member for effecting displacement of the nozzle.
The beams may be anchored at one end to an anchor mounted on, and extending upwardly from, the substrate and connected at their opposed ends to the connecting member. The connecting member may comprise an arm having a first end connected to the actuator with the nozzle connected to an opposed end of the arm in a cantilevered manner. Thus, a bending moment at said first end of the arm is exaggerated at said opposed end to effect the required displacement of the nozzle.
The printhead may include a plurality of nozzles each with their associated actuators and connecting members, arranged on the substrate. Each nozzle, with its associated actuator and connecting member, may constitute a nozzle assembly.
The printhead may be formed by planar monolithic deposition, lithographic and etching processes and, more particularly, the nozzle assemblies may be formed on the printhead by these processes.
The substrate may include an integrated drive circuit layer. The integrated drive circuit layer may be formed using a CMOS fabrication process.